Internet access is becoming ubiquitous and the means by which the access is obtained varies widely. For example, the internet access may be through a Digital Subscriber Line (DSL), a cable modem, a fiber optic network, a wireless communication network, etc. When the internet service provides high data rates it is often referred to as broadband internet service. Broadband internet service is generally understood to be a service that is always on and offers data rates in the order of mega-bits per second for both download and upload.
A client device as defined in the present disclosure is a device that may access the internet from one or more of the sources from which the internet service may be available. Such client devices may include conventional devices such as a smartphone, a tablet, a feature-phone, a laptop or a desktop personal computer, etc. Other client devices may include devices that are embedded within devices that perform other functions such as an entertainment system in a home or in an automobile, a home appliance such as a refrigerator or washer/dryer, a wristwatch with a heart rate monitor, a medical device such as a blood pressure meter or insulin sensor, a utility meter, a gaming console, a camera, a navigation device, an industrial equipment, etc. These types of devices are collectively referred herein as machine type client devices.
These diverse types of client devices may access the internet service directly through one of the sources of primary internet access mentioned earlier. Alternatively, the client devices may access the internet through a local network that performs distribution of the primary internet access to the users localized in a given area. Examples of such local networks include Local Area Network (LAN) using Ethernet, Wireless LAN (WLAN) commonly known as Wi-Fi, Bluetooth™, or some other local area networking schemes. Such short range wireless networks are referred herein as Short Range Wireless Links (SRWL). When a client device is in the proximity of a location where such a SRWL access is available, it may access the internet using the SRWL. FIG. 1 illustrates an example scenario of client devices accessing internet over a WLAN SRWL, which is connected to a traditional wire-line internet service such as DSL or cable modem. The local area where WLAN service is available is often referred to as Hotspot. The device that offers the WLAN service in a given local area is referred to as an Access Point (AP). In the present disclosure, the terms Hotspot AP or Hotspot are used interchangeably to refer to the device that offers the WLAN service in a given local area.
A Hotspot AP may be connected to DSL or cable modem through any of the standardized interfaces such as Universal Serial Bus (USB), Ethernet, or proprietary interfaces. In some cases, the DSL or cable modem and the Hotspot AP may be part of a single physical device. In such cases the interface between the DSL or cable modem and AP may use Secure Digital Input Output (SDIO) or other suitable interface.
Client devices may also obtain internet access over mobile wireless communication networks. These mobile wireless networks are often referred to as Wireless Wide Area Network (WWAN). The internet service offered by such networks is often referred to as mobile broadband internet or Mobile Broadband (MB) and the mobile wireless networks are often referred to as mobile broadband networks. The terms WWAN and MB are used interchangeably herein.
As the variety of client devices has increased and the demand for MB access has increased, a device known as a mobile Hotspot is commonly used. A mobile Hotspot device may include both a modem for MB access and a WLAN AP (Hotspot AP) to distribute the internet to local client devices. FIG. 2 illustrates the block diagram of an example mobile Hotspot device. As shown in FIG. 2, for the chosen example, the MB modem and the Hotspot AP may be connected to each other via one of the standard interfaces used in the industry such as USB, SDIO, or proprietary interfaces. In another mobile Hotspot example, the MB modem and the WLAN AP may be a single Integrated Circuit (IC) as shown in FIG. 3.
Some mobile Hotspot devices may serve as a single function device, i.e., they only perform the mobile Hotspot function. Such mobile Hotspots may take many different form factors such as a mobile Hotspot integrated into an automobile, a standalone device that can be carried around with or without a battery, integrated into an accessory device for a tablet, a standalone device that can be powered by a wall outlet, etc.
Some client devices have multiple capabilities and being a Hotspot is one of the capabilities. For example, a smartphone may have a mobile broadband modem that may be used to get mobile internet service directly from the mobile broadband network as illustrated in FIG. 4. The flow of data is as shown in FIG. 4 from the mobile broadband modem to the application processor that processes the download and upload data and interacts with the user via the display and other elements of the user interface such as audio, vibration, etc. The smartphone may also have a WLAN modem to access internet service over a Hotspot AP. When it is in the vicinity of a Hotspot AP, it may use internet service from the Hotspot as illustrated in FIG. 1. In another smartphone example, the mobile broadband modem, the WLAN AP and the Application Processor may be integrated into a single Integrated Circuit (IC) as shown in FIG. 5.
A smartphone may also serve as a mobile Hotspot to provide internet service over WLAN to other client devices in its vicinity. FIG. 6 illustrates an example scenario where the smartphone serves as a mobile Hotspot and provides internet service to a machine type client device which may have only a WLAN access. In another smartphone mobile Hotspot example, the mobile broadband modem, the WLAN AP and the Application Processor may be integrated into a single IC as shown in FIG. 7.
An example of a mobile broadband network is the Long Term Evolution (LTE) from the 3rd Generation Partnership Project (3GPP). The LTE technology and its evolution are often referred to as fourth generation (4G) technologies. A client device may also use any of the previous generation technologies such as “2G”, “3G” from 3GPP and other standardization bodies. A client device may also use future generation technologies for Hotspot, mobile Hotspot, and mobile networks.
Although a Hotspot or mobile Hotspot may be able to obtain internet service and distribute it to multiple client devices in a given local area, it may not be able to provide other key services that users commonly use. For example, voice calls and SMS based text messaging remain two of the most commonly used applications in client devices. A client device accessing internet through a Hotspot or mobile Hotspot may still be receiving voice calls or SMS based text messages directly through the WWAN as illustrated in FIG. 8. Four interconnected networks are shown in FIG. 8: Public Switch Telephone Network (PSTN) 802, WWAN 804, internet 806, and WLAN (Hotspot) 808. The PSTN is connected to the WWAN through the interface 820 and to the internet through the interface 822. The WWAN and internet are connected through the interface 818. The Cable modem 812 is connected to the internet through the interface 824. These interfaces may use open industry standards or may use proprietary standards. The Hotspot, in the present example, is connected to the internet using a Cable modem interface. In the present example, the Smartphone 811 is connected to the Hotspot Access Point 810 for internet service through the Cable modem 812. Simultaneously, it is also connected to the WWAN 804 for voice calls and SMS based text messaging. The Smartphone 811 may exchange SMS based text messages with the Smartphone 814 over the WWAN 804. The Smartphone 811 may have voice calls with the landline phone 816 through WWAN 804 and PSTN 802. The cordless phone 826 may access the conventional landline voice service through the cordless base 828 which in turn is connected to the PSTN 802 though the conventional landline interface 830. The coverage area 808 of the WLAN Hotspot and the coverage area 832 of the cordless base 832 may partially or fully overlap.
Although aspects of the present disclosure are illustrated using a particular type of mobile Hotspot, the disclosure may be applicable to other types of mobile Hotspot devices, some of which are listed in an earlier section of the present disclosure. In the remainder of the present disclosure a mobile Hotspot is used as an example. A mobile Hotspot may obtain the primary internet service through a cable modem, DSL or MB modem. When a mobile Hotspot is an area where it may receive primary internet service from cable modem or DSL, it may use the internet service from that source. When a mobile Hotspot is an area where it does not have access to receive primary internet service from cable modem or DSL, it may use the internet service from WWAN. When a client device is receiving internet service from a mobile Hotspot, it may still be connected to the WWAN for receiving other services such as voice calls, SMS, etc.
Typically, as shown in FIG. 9, a WWAN comprises elements such as client devices or mobile stations and one or more base stations. Other network devices may also be employed, such as a mobile switching center (not shown). As illustrated in FIG. 9, the communication path from the base station (BS) to the client device or mobile station (MS) is referred to herein as a downlink (DL) direction or downlink channel. The communication path from the client device to the base station is referred to herein as an uplink (UL) direction or uplink channel. In some wireless communication systems, the MS communicates with the BS in both the DL and UL directions. For instance, such communication is carried out in cellular telephone systems. In other wireless communication systems, the client device communicates with the base stations in only one direction, usually the DL. Such DL communication may occur in applications such as paging. Typically in a wireless communication system, the client device and the base station may transmit information in blocks of data and such a block of data is referred herein as a “message.”
A base station to which the client device may be downlink synchronized and/or communicating with at any given time is referred herein as the Serving Base Station (SBS). In some wireless communication systems the serving base station may be referred to as the serving cell. The base stations that are in the vicinity of the serving base station are called Neighbor Base Stations (NBS). Similarly, in some wireless communication systems a neighbor base station may be referred to as a neighbor cell.
A client device, after initially synchronizing with a cell, may switch to another cell depending on the signal conditions, network congestion, and other criteria. The process of switching from one cell to another cell by a client device is often referred to as handover (HO) or cell reselection. In some wireless communication systems handover is also referred to as handoff. Also in some wireless communication systems cell reselection is also referred to as idle mode handoff. An NBS, to which a client device may be switching over its communication from the current SBS, is herein referred to as Target Base Station (TBS). In some wireless communication systems, a target base station is normally referred to as a target cell. Sometimes, during a handover, the serving cell and the target cell may be the same and only the channel used for communication may be changed. Such a handover, in which the cell is not changed, is called an intra-cell handover. The purpose of intra-cell handover may be that the new channel is better suited for communication than the previous channel within the same cell. Cell reselections or handovers amongst cells that use the same frequency are referred herein as intra-frequency cell reselection or handover. Cell reselections or handovers amongst cells that use different frequencies are referred herein as intra-frequency cell reselection or handover. A network may use different Radio Access Technologies (RATs) for providing various services. In a particular network, the cells of different RAT types may be overlapping or adjacent to each other. If a neighbor cell is using a RAT type that is different from the RAT type used by the serving cell, it is referred to as an inter-RAT neighbor cell.
The decision making process for handovers and cell reselections varies from one wireless communication system to another. However, the decisions are generally based on the signal conditions measurements by the client devices and reporting of those measurements to the wireless communication network by the client devices. The wireless communication network generally may influence and control the measurements and reporting process of the client device by providing parameters for the measurement and reporting process. The actual decision to perform handover may be made either by the wireless communication network or by the client device depending on the type of particular wireless communication system. On the other hand the cell reselection decisions in idle mode (i.e., when client device is not in active communication with the wireless communication network) may be generally performed autonomously by the client device. Both handovers and cell reselections may normally lead to change of cell from which the client device may access communication services. The difference between the handover procedure and cell reselection procedure depends generally on whether a client device is engaged in an active communication with the wireless communication network.
Normally, certain types of system information may be required by all client devices so that they may communicate with the wireless communication network. The system information typically includes system synchronization information, system parameters, resource allocation information, paging information, etc. The wireless communication network may transmit such system information as broadcast data so that all client devices within its coverage area may be able to receive. Such information is herein referred to as “broadcast messages.”
Typically in a wireless communication system a base station may group the system information and each group of system information may be transmitted as multiple broadcast messages and such broadcast messages are herein referred as system parameter messages. The system parameter messages may carry important system information without which the client device may not be able to communicate with the wireless communication network. The wireless communication network may transmit these system parameter messages at regular intervals in such a way that any client device that enters its coverage area may receive these system parameter messages and may be able to communicate with the wireless communication network at the earliest possible time. Client devices that are already in the base station's coverage area may also periodically receive these system parameter messages for possible updates. Normally a client device may store the system parameter messages in its memory for the current SBS.
Typically, in wireless communication systems, most of the system parameter messages may not change frequently. For example, some system parameter messages may change once or twice a day and some system parameter messages may not change for many days.
In some wireless communication systems, when a client device switches to a new base station due to cell reselection or handover, it may be required to receive the system parameter messages for the new SBS and certain system parameter messages for the selective list of NBSs corresponding to the new SBS.
The set of all system parameter messages broadcast by a base station is herein referred to as “base station broadcast system information.” The individual block of system information message may be referred to as System Information Block (SIB). Two or more SIBs may be grouped and sent as a single System Information (SI) message. There may be different SIBs describing different groups of system parameters such as SIB Type1 (SIB1), SIB Type2 (SIB2), etc. The SI for one or more cells may be periodically updated by the network. To ensure that the client devices are using the correct version of the SI, a field referred herein as “change-mark” is generally included in the SI messages. Client devices may store the change-mark of the SIs it has decoded. If the new SI is transmitted by a cell, it may increment the change-mark to enable the client terminal to detect that it needs to acquire the newly updated SI. The change-mark of the newly acquired SI is then used as latest version for detecting any future changes in the SI. The change-mark field may be incremented in modulo arithmetic to keep the field bit-width to a minimum. For example, the change-mark may be incremented modulo-8 and the value may be represented by a 3-bit wide field.
In idle mode, a client device for the most part may turn off a majority of its circuitry to reduce power consumption. This is often referred to as “sleep” state, a sub-state within the idle mode. A client device may remain in a sleep state for a long duration and may wake up at the desired time window where it expects to receive the paging messages and certain SIBs. This alternating sequence of sleep and wake-up in idle mode is referred herein as Discontinuous Reception (DRX). The sleep and wake-up sequence may follow regular pattern and its period is often referred to as DRX cycle. The success rate for the incoming calls (e.g., mobile terminated voice calls and/or data calls) in a client device is directly related to the successful reception of paging messages. Normally, in idle mode, in addition to the reception of paging messages and SIB messages, a client device may continue to search and monitor neighbor cells.
When a client device performs a network registration procedure to get service from a cell, it decodes the system information broadcast in the cell. The client device may store such system information. The system information carries important information regarding the cell reselection criteria. Such information includes but not limited to the tracking area identity (TAI), Public Land Mobile Network Identity (PLMN ID) which uniquely identifies a particular network operator, Closed Subscriber Group Identity (CSG ID), RAT type, neighbor cell frequencies, etc. This information may help to decide whether a cell is a “suitable cell” for the client device to avail all the services offered by it, or the cell is an “acceptable cell” where the client device may avail only limited services such as emergency calls. The client device may have to perform the network registration procedure to get service from the network and for the network to be able to page the client device for mobile terminated (incoming) calls. The network registration procedure may be typically performed by a client device with a particular cell. A group of cells in the geographic vicinity of each other may form a registration area. A registration area may be identified based on the system information of a cell. For example, the TACs of a group of cells in a registration area may be the same.
Each base station in a wireless communication network may be identified by a unique identifier referred to herein as Cell Identity (CID). The CID of a base station may become known to a client device when it decodes SI from the base station. To avoid unnecessary updates from a client device and yet ensure the ability to reach a client device at any given time, the network may organize a group of cells into a “tracking area” and use a Tracking Area Identity (TAI) to identify the various groups of cells. This is illustrated in FIG. 10 where four different tracking areas are illustrated. A cell may broadcast information about the tracking area it belongs to by including the TAI information in the system information. A client device may be required to inform the network when it begins to receive service from a cell that belongs to a tracking area that is different from the tracking area of the cells from which it was previously receiving service. The process of informing the network that the client device has begun receiving service from a cell that belongs to a new tracking area is referred herein as Tracking Area Update (TAU) procedure. With this method, a client device performs TAU only when there is a change in TAI of the cell from which it is getting service. For example, in FIG. 10, when a client device reselects from the cell with CID=1003 to the cell with CID=1007 which has the same TAI, it may not perform TAU procedure. However, when the client device reselects from the cell with CID=1007 and TAI=200 to the cell with CID=1012 and TAI=201, it may perform TAU procedure.
As long as a client device is in the same registration area, the client device may not perform network registration procedure again except that a periodic network registration update procedure may need to be performed even if the client device continues to move within the same registration area. If the client device moves to a cell which does not belong to the registration area in which the client device is registered, then the client device may perform network registration procedure to get access to and service from the network.
When a client device is in idle mode, the network may only be aware of the location of the client device at the registration area level. In order for a network to page a client device, it may need to send the paging message in all cells belonging to the same registration area. The instances for paging message transmission, known as paging occasions (POs), are usually derived based on a client device's unique identity and a paging cycle. The network may transmit a paging message addressed to a specific client device in its specific paging occasion. When a client device performs cell reselection, the exact instances of paging occasions may be different in the new serving cell. Depending on the exact timing of the cell reselection and the timing of the POs in the old serving cell and the new serving cell, the client device may potentially miss a paging message or may receive it with delay.
When a client device is connected to a mobile Hotspot for internet service, it still may be connected to a WWAN for other services such as voice and SMS. The client device and the mobile Hotspot may be camped on the same cell of the same WWAN, and both the devices may be decoding the same broadcast information (SIBs). This may be a redundant reception since most of the client devices which are connected to the mobile Hotspot may be camped on the same cell of the same WWAN.